Question

For example I want to declare

let len, (*mutable*) i =
            if s.Length >= 2 && s.[0] = '0' && (s.[1] = 'x' || s.[1] = 'X') then
                (s.Length - 2, 2)
            else (s.Length, 0)

constant binding len and mutable i, is it possible ?

Added :
I will use references then

    let len, i =
        if s.Length >= 2 && s.[0] = '0' && (s.[1] = 'x' || s.[1] = 'X') then
            (s.Length - 2, ref 2)
        else (s.Length, ref 0)

Answer 1

No. mutable applies to the entire let binding. You’ll have to do:

let len, i = ...
let mutable i = i